One of the challenges of buying local advertising is, how do you know if it worked? How do you know if it's got value? We're moving toward an e-commerce experience for local, an Amazon-like experience for local.

The entrepreneurs that really make it are the ones that start with an idea but are ready to change it at a moment's notice.

Starting a company, your success is going to be very dependent on how you adapt. You're going to make decisions, you're going to make bets; most of them are going to turn out to be wrong.

In early 2008, it was confirmed that there would be an opportunity to build applications for the iPhone. We were fortunate enough to make the right call on that: to bet early, to put resources into it and have a pretty good application in the store at the moment when it opened.

Theres simply anger over the accountability that Yelp brings and also this feeling of powerlessness because so much power is now being put in the hands of the consumer. But the important thing that gets lost with some of these business owners who are very upset with us is its the whole picture that counts.

In the very beginning, Yelp started as a service where we really didn't think people would write reviews for fun. The whole concept of user-generated content was pretty nascent in 2004.

When Yelp first took off, our rankings on Google would fluctuate wildly.